Problem - Kevin Tafuro

case '\b': *ptr++ = '\\'; *ptr++ = 'b'; break;
case '\n': *ptr++ = '\\'; *ptr++ = 'n'; break;
case '\r': *ptr++ = '\\'; *ptr++ = 'r'; break;
case '\t': *ptr++ = '\\'; *ptr++ = 't'; break;
default:
*ptr++ = *c;
break;
}
}
*ptr++ = quote;
*ptr = 0;
return out;
}
3.12 Detecting Illegal UTF-8 Characters
Problem
Your program accepts external input in UTF-8 encoding. You need to make sure that
the UTF-8 encoding is valid.
Solution
Scan the input string for illegal UTF-8 sequences. If any illegal sequences are
detected, reject the input.
Discussion
UTF-8 is an encoding that is used to represent multibyte character sets in a way that
is backward-compatible with single-byte character sets. Another advantage of UTF-8
is that it ensures there are no NULL bytes in the data, with the exception of an actual
NULL byte. Encodings such as Unicode’s UCS-2 may (and often do) contain NULL
bytes as “padding” if they are treated as byte streams. For example, the letter “A” is
0x41 in ASCII or UTF-8, but it is 0x0041 in UCS-2.
The first byte in a UTF-8 sequence determines the number of bytes that follow it to
make up the complete sequence. The number of upper bits set in the first byte minus
one indicates the number of bytes that follow. A bit that is never set immediately follows
the count, and the remaining bits are used as part of the character encoding.
The bytes that follow the first byte will always have the upper two bits set and unset,
respectively; the remaining bits are combined with the encoding bits from the other
bytes in the sequence to compute the character. Table 3-2 lists the binary encodings
for the range of characters from 0x00000000 to 0x7FFFFFFF.
110 | Chapter 3: Input Validation
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